Anomalies in the ultrahigh-temperature elastic moduli and internal frictions of Ti-6Al-4V alloys revealed by M-PUCOT

Although titanium alloys can be operative at high temperatures up to 700 degrees C , their mechanical properties at ultrahigh temperatures are not well studied. In this work, an automatic testing system is designed for the modified piezoelectric ultrasonic composite oscillator technique (M-PUCOT) to measure the elastic moduli and internal frictions of two different Ti-6Al-4V alloys from room temperature to 1200 degrees C . The results show that for the as-received Ti-6Al-4V (with standard heat treatment), which contains an equiaxed alpha phase and a small amount of the beta phase, a large internal friction peak due to the phase transition ( alpha+ beta - beta) is observed for the first time. However, for the Ti-6Al-4V annealed at 1200 degrees C , no phase transition peak is observed; instead, a weak Debye-type peak is observed. Moreover, the elastic moduli and hardness are significantly enhanced, which is attributed to the increase in interstitial oxygen atoms and the complete formation of the Widmanstatten alpha structure. (c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

In this study, an automatic testing system is designed to measure the mechanical properties of two different Ti-6Al-4V alloys at high temperatures using the modified piezoelectric ultrasonic composite oscillator technique. The results show variations in internal friction and elastic moduli under different heat treatment conditions.